drm: Don't test reused states

We shouldn't need to test state, because the state that worked previously
should work again. However, to be completely safe against unpredictable
edge cases, we've kept a state check.

Remove that check and instead force a state rebuild in the case of an
application failure.

Keep track of how often this happens so we can fall back to checking
instead of consistently failing state application.

fixes #1081

Signed-off-by: Derek Foreman <derek.foreman@collabora.com>

libweston/backend-drm/drm-internal.h

@@ -82,6 +82,8 @@
 #define MAX_DMABUF_PLANES 4
 #endif
 
+#define DRM_MAX_REUSE_FAILURES 10
+
 /**
  * A small wrapper to print information into the 'drm-backend' debug scope.
  *
@@ -240,6 +242,8 @@ struct drm_device {
 
 	/* struct drm_colorop_3x1d_lut::link  */
 	struct wl_list drm_colorop_3x1d_lut_list;
+
+	int reused_state_failures;
 };
 
 struct drm_backend {
@@ -664,6 +668,9 @@ struct drm_output {
 	submit_frame_cb virtual_submit_frame;
 
 	enum wdrm_content_type content_type;
+
+	bool reused_state;
+	bool force_rebuild_state;
 };
 
 void

libweston/backend-drm/drm.c

@@ -1201,6 +1201,7 @@ drm_repaint_flush_device(struct drm_device *device)
 	struct drm_pending_state *pending_state;
 	struct weston_output *base;
 	int ret;
+	bool failed_reuse = false;
 
 	pending_state = device->repaint_data;
 	if (!pending_state)
@@ -1222,7 +1223,27 @@ drm_repaint_flush_device(struct drm_device *device)
 		if (!base->will_repaint || !tmp || tmp->device != device)
 			continue;
 
-		if (ret == -EBUSY)
+		/* We shouldn't be failing at all when using a previous state,
+		 * and when we do it can lead to choppy frame scheduling.
+		 * Keep track of any failures and if we have a few, just give
+		 * up on ever reusing state.
+		 */
+		if (tmp->reused_state) {
+			failed_reuse = true;
+			tmp->force_rebuild_state = true;
+			device->reused_state_failures++;
+		}
+	}
+
+	if (failed_reuse)
+		drm_debug(b, "[repaint] failed with reused state, will rebuild and try again.\n");
+
+	wl_list_for_each(base, &b->compositor->output_list, link) {
+		struct drm_output *tmp = to_drm_output(base);
+		if (!base->will_repaint || !tmp || tmp->device != device)
+			continue;
+
+		if (ret == -EBUSY || failed_reuse)
 			weston_output_schedule_repaint_restart(base);
 		else
 			weston_output_schedule_repaint_reset(base);

libweston/backend-drm/state-propose.c

@@ -1033,6 +1033,11 @@ drm_output_propose_state_try_reuse(struct weston_output *output_base,
 	struct weston_paint_node *pnode;
 	struct drm_output_state *state;
 
+	if (output->force_rebuild_state) {
+		debug_propose_fail(output, mode, "previous state failed");
+		return NULL;
+	}
+
 	/* These states are where we end up when we can't use planes
 	 * at all, sometimes simply because we don't have a renderer
 	 * fb yet. In that case we'd immediately get into a better
@@ -1139,10 +1144,13 @@ drm_output_propose_state_try_reuse(struct weston_output *output_base,
 						pnode->surface->buffer_release_ref.buffer_release);
 	}
 
-	if (drm_pending_state_test(pending_state) != 0) {
-		debug_propose_fail(output, mode, "atomic test not OK");
-		drm_output_state_free(state);
-		return NULL;
+	if (device->reused_state_failures > DRM_MAX_REUSE_FAILURES) {
+		drm_debug(b, "\t\t[reuse] must test due to high number of failures\n");
+		if (drm_pending_state_test(pending_state) != 0) {
+			debug_propose_fail(output, mode, "atomic test not OK");
+			drm_output_state_free(state);
+			return NULL;
+		}
 	}
 
 	/* In any state with the renderer, we need to unreference and remove
@@ -1163,6 +1171,7 @@ drm_output_propose_state_try_reuse(struct weston_output *output_base,
 		pstate->fb = NULL;
 	}
 
+	output->reused_state = true;
 	return state;
 }
 
@@ -1192,6 +1201,8 @@ drm_output_propose_state(struct weston_output *output_base,
 	/* Record the current lowest zpos of the underlay plane */
 	uint64_t current_lowest_zpos_underlay = DRM_PLANE_ZPOS_INVALID_PLANE;
 
+	output->reused_state = false;
+
 	if (mode & DRM_OUTPUT_PROPOSE_STATE_REUSE) {
 		return drm_output_propose_state_try_reuse(output_base,
 							  pending_state,
@@ -1603,6 +1614,8 @@ drm_assign_planes(struct weston_output *output_base)
 	assert(state);
 	assert(state->planes_enabled == !output_base->disable_planes);
 
+	output->force_rebuild_state = false;
+
 	drm_debug(b, "\t[repaint] Using %s composition\n",
 		  drm_propose_state_mode_to_string(mode));